1. Field of the Invention
The present invention relates to a low noise amplification microwave integrated circuit (hereinafter MIC) for use in a satellite broadcasting receiving converter or microwave communication, and more particularly to an improvement in an input matching characteristic thereof
2. Related Background Art
One of prior art low noise amplification MICs uses a monolithic MIC (hereinafter MMIC) which uses a field effect transistor such as a GaAs FET. A general circuit configuration of the MMIC is shown in FIG. 1 in which a source of a FET 21 is grounded, an input matching circuit 22 is connected to an input terminal of MMIC and an output matching circuit 23 is connected to an output terminal of MMIC.
In an input matching characteristic of an initial stage amplifier in a multi-stage amplification MMIC circuit, either a noise matching characteristic which requires a low noise characteristic is important or a gain matching characteristic which requires a high gain characteristic is important, depending on an application of the circuit. Constants of elements in the input matching circuit 22 are set in accordance with the characteristic.
In the prior art MMIC, the matching characteristic of the initial stage amplifier has been designed by taking primary consideration of only one of the noise matching characteristic and the gain matching characteristic, depending on the application. The circuit designed primarily for the noise matching characteristic can provide a minimum noise figure (hereinafter NF) but a gain of the initial stage amplifier is low and an input voltage standing wave ratio (hereinafter VSWR) is high.
In the circuit designed primarily for the gain matching characteristic, the gain of the initial stage
is high and the input VSWR is low, but the NF is high.